Computational program "Crystal-2" in Visual Basic 6.0 was designed and applied to identify the specification for three crystal structures includes the lattice parameters (a, b, c), the axial angles (?, ?, ?), the Filling Factor(FF) foe CdS, the Average Grain Size (AGS) for CdS, and the Elastic Strain (?) for CdS and CdTe. This program will give us a complete description on crystal structure for three crystal structures material by inserting a data which include the values of Miller indices (hkl), the diffracted angle (2?) from ASTM data for cadmium sulfide, beryllium and compare the calculated values with the values of ASTM data used material. This program is includes many special calculations for a certain material such as cadmium sulfide that used to examine the cubic system and calculated lattice parameters were found to be a ? 5.82 Å, b ? 5.83 Å and c ? 5.81 Å and there is a drift error about D ? 4.365314 10 Å when is compared with the published values, and to examine orthorhombic system by using ASTM data for cadmium sulfide as example the calculated values were found to be a ?4.169 Å, b ? 2.791 Å and c ? 5.413 Å, with a drift error about D ? 8.28014 10 Å, also the tetragonal system is also examined for beryllium and the calculated values were found to be a ? 1.36 Å, b ? 1.36 Å, and c ? 3.58 Å with a drift error D ? 5.743535 10 Å, and the average grain size is also calculated for CdS by using the Scherrer's formula ,the filling factor is determined for Cadmium Sulfide, and the elastic strain by using the Hall-Williamson method for CdS and CdTe.